Surgical tool positioning based on sensed parameters

ABSTRACT

Devices, systems, and methods are provided in which movement of a tool is controlled based on sensed parameters. In one embodiment, an electromechanical tool is provided having an instrument shaft and an end effector formed thereon. The electromechanical tool is configured to be mounted on an electromechanical arm, and the electromechanical tool is configured to move with or relative to the electromechanical arm and perform surgical functions. A controller is operatively coupled to the electromechanical arm and the electromechanical tool and is configured to retard advancement of the electromechanical tool toward a tissue surface based on a sensed amount of displacement of a tissue surface, a strain on the tissue of the patient, the temperature of the electromechanical tool, or the like.

FIELD OF THE INVENTION

Methods and devices are provided for robotic surgery, and in particularfor positioning surgical tools based on sensed parameters.

BACKGROUND OF THE INVENTION

Minimally invasive surgical (MIS) instruments are often preferred overtraditional open surgical devices due to the reduced post-operativerecovery time and minimal scarring. Laparoscopic surgery is one type ofMIS procedure in which one or more small incisions are formed in theabdomen and a trocar is inserted through the incision to form a pathwaythat provides access to the abdominal cavity. The trocar is used tointroduce various instruments and tools into the abdominal cavity, aswell as to provide insufflation to elevate the abdominal wall above theorgans. The instruments and tools can be used to engage and/or treattissue in a number of ways to achieve a diagnostic or therapeuticeffect. Endoscopic surgery is another type of MIS procedure in whichelongate flexible shafts are introduced into the body through a naturalorifice.

Although traditional minimally invasive surgical instruments andtechniques have proven highly effective, newer systems may provide evenfurther advantages. For example, traditional minimally invasive surgicalinstruments often deny the surgeon the flexibility of tool placementfound in open surgery. Difficulty is experienced in approaching thesurgical site with the instruments through the small incisions.Additionally, the added length of typical endoscopic instruments oftenreduces the surgeon's ability to feel forces exerted by tissues andorgans on the end effector. Furthermore, coordination of the movement ofthe end effector of the instrument as viewed in the image on thetelevision monitor with actual end effector movement is particularlydifficult, since the movement as perceived in the image normally doesnot correspond intuitively with the actual end effector movement.Accordingly, lack of intuitive response to surgical instrument movementinput is often experienced. Such a lack of intuitiveness, dexterity andsensitivity of endoscopic tools has been found to be an impediment inthe increased the use of minimally invasive surgery.

Over the years a variety of minimally invasive robotic systems have beendeveloped to increase surgical dexterity as well as to permit a surgeonto operate on a patient in an intuitive manner. Telesurgery is a generalterm for surgical operations using systems where the surgeon uses someform of remote control, e.g., a servomechanism, or the like, tomanipulate surgical instrument movements, rather than directly holdingand moving the tools by hand. In such a telesurgery system, the surgeonis provided with an image of the surgical site on a visual display at alocation remote from the patient. The surgeon can typically perform thesurgical procedure at the location remote from the patient whilstviewing the end effector movement on the visual display during thesurgical procedure. While viewing an image of the surgical site on thevisual display, the surgeon performs the surgical procedures on thepatient by manipulating master control devices at the remote location tocontrol motion of the remotely controlled instruments.

While significant advances have been made in the field of roboticsurgery, there remains a need for improved methods, systems, and devicesfor use in robotic surgery.

SUMMARY OF THE INVENTION

Surgical devices, systems, and methods are provided for positioningsurgical tools based on sensed parameters. In one embodiment, a surgicalsystem can include one or more of the following components. The surgicalsystem can include an electromechanical arm configured for movement inmultiple axes, and an electromechanical tool having an instrument shaftand an end effector formed thereon. The electromechanical tool can beconfigured to be mounted on the electromechanical arm, and theelectromechanical tool can be configured to move with or relative to theelectromechanical arm and to apply energy to tissue engaged by the endeffector. The surgical system can also include a controller operativelycoupled to the electromechanical arm and the electromechanical tool. Thecontroller can be configured to retard advancement of theelectromechanical tool toward a tissue surface based on a sensedtemperature of the end effector.

In some variations, one or more of the features described herein may beincluded in the system. A sensor can be provided and it can beconfigured to sense the temperature of the end effector. The sensor caninclude an infrared (IR) sensor, a thermocouple disposed on the endeffector, a camera, or the like. In other aspects, the surgical systemcan include a sensor configured to sense a position of the end effectorrelative to a tissue surface.

The controller can be configured to retard advancement of theelectromechanical tool when the temperature is within a predeterminedthreshold temperature, predetermined threshold distance from a tissuesurface, or the like. The threshold distance can be a function of thetemperature of the end effector. The system can also include a sensorconfigured to sense a distance of the end effector from a tissuesurface.

In another aspect, a method for operating a system is provided andincludes applying energy to a tissue using an end effector formed on aninstrument shaft of an electromechanical tool. The electromechanicaltool can be mounted on an electromechanical arm. A sensed temperature ofthe end effector can be received during an application of the energy tothe tissue. A velocity of the electromechanical tool, toward a tissuesurface, can be reduced based on the sensed temperature.

In some variations, one or more of the following operations may beincluded in the method. The sensed temperature can be a sensedtemperature of the end effector and a sensed temperature of the tissuesurface. The velocity can be reduced to a first threshold velocity whenthe temperature is within a first predetermined temperature range, asecond threshold velocity when the temperature is within a secondpredetermined temperature range, or the like. The first thresholdvelocity can be adjusted by a first amount in response to determiningthat the electromechanical tool is a first threshold distance from thetissue surface. The first threshold velocity can be adjusted by a secondamount in response to determining that the electromechanical tool is asecond threshold distance from the tissue surface.

The velocity can be reduced based on a sensed position of the endeffector relative to the tissue surface. The temperature can be sensedby a sensor on the end effector, a sensor on a camera, or the like.

In another aspect, a surgical system is provided having anelectromechanical arm configured for movement in multiple axes. Thesurgical system can include an electromechanical tool having aninstrument shaft and an end effector formed thereon. Theelectromechanical tool can be configured to be mounted on theelectromechanical arm, and the electromechanical tool can be configuredto move with or relative to the electromechanical arm and to applyenergy to tissue engaged by the electromechanical tool. The surgicalsystem can include a controller operatively coupled to theelectromechanical arm and the electromechanical tool. The controller canbe configured to retard advancement of the electromechanical tool towarda tissue surface based on a sensed amount of displacement of a tissuesurface.

In some variations, one or more of the following features can beincluded in the surgical system. For example, the surgical system caninclude an applicator having a material configured to be applied onto atissue surface, the material being configured to indicate a displacementof the tissue surface. In one embodiment, the material can include abio-absorbable aerosolized particulate material. In other aspects, thesensed amount of displacement can include a strain of the tissuesurface. The controller can be configured to retard advancement of theelectromechanical tool when the sensed amount of displacement is withina predetermined displacement range.

The system can include a sensor configured to sense an amount ofdisplacement of a tissue surface. The sensor can include a camera.

In another aspect, a method is provided that includes advancing an endeffector formed on an instrument shaft of an electromechanical tooltoward a tissue surface. The electromechanical tool can be mounted on anelectromechanical arm. A sensed amount of displacement of the tissuesurface can be received and, based on the sensed amount of displacement,a velocity of the electromechanical tool toward a tissue surface can bereduced.

In some variations, one or more of the following operations and featurescan be included in the method. The sensed amount of displacement can beobtained by detecting movement of a patterned material deposited ontothe tissue surface. The patterned material can provide at least twocontrast points. The method can include determining a tissue strainbased on the detected movement of the patterned material.

The velocity of the electromechanical tool can be reduced when thesensed amount of displacement exceeds a threshold amount ofdisplacement. The velocity of the electromechanical tool can be reducedto a first threshold velocity when the amount of displacement is withina first predetermined displacement range, to a second threshold velocitywhen the amount of displacement is within a second predetermineddisplacement range, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a perspective view of one embodiment of a surgical roboticsystem having a patient-side portion and a user-side portion;

FIG. 2 is a perspective view of one embodiment of a surgical tool withan end effector in the vicinity of patient tissue;

FIG. 3 is a perspective view of the surgical tool of FIG. 2 in thevicinity of tissue;

FIG. 4 is a graphical depiction of jaw temperature changes of an endeffector over time and jaw proximity changes to patient tissue over timeof the end effector of FIG. 2;

FIG. 5 is a perspective, partially transparent view of anotherembodiment of an end effector;

FIG. 6 is a schematic illustrating one exemplary process flow for oneembodiment of using an end effector;

FIG. 7 is a perspective view of one embodiment of a surgical tool withan end effector in the vicinity of patient tissue; and

FIG. 8 is a diagram depicting a computer system for facilitating controlof a robotic surgical system.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the devices andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

Further, in the present disclosure, like-named components of theembodiments generally have similar features, and thus within aparticular embodiment each feature of each like-named component is notnecessarily fully elaborated upon. Additionally, to the extent thatlinear or circular dimensions are used in the description of thedisclosed systems, devices, and methods, such dimensions are notintended to limit the types of shapes that can be used in conjunctionwith such systems, devices, and methods. A person skilled in the artwill recognize that an equivalent to such linear and circular dimensionscan easily be determined for any geometric shape. Sizes and shapes ofthe systems and devices, and the components thereof, can depend at leaston the anatomy of the subject in which the systems and devices will beused, the size and shape of components with which the systems anddevices will be used, and the methods and procedures in which thesystems and devices will be used.

Various surgical systems for positioning surgical tools based on sensedparameters are provided. Robotic surgical tools, such aselectromechanical tools, generally have an instrument shaft and an endeffector on a distal end thereof. The electromechanical tool isconfigured to be mounted on an electromechanical arm, and theelectromechanical tool is configured to move with or relative to theelectromechanical arm and to perform surgical functions. The tool has aplurality of actuators for causing various functions of the endeffector, such as rotation, articulation, clamping, energy delivery,etc. The electromechanical arm can electromechanically drive theactuators to control the end effector.

Electromechanical arms and electromechanical tools provided herein havevarious controllers and mechanisms for retarding advancement of theelectromechanical tool toward a tissue surface based on a sensed amountof displacement of a tissue surface, a strain on the tissue of thepatient, a temperature of the electromechanical tool, or the like.

As will be appreciated by a person skilled in the art, electroniccommunication between various components of a robotic surgical systemcan be wired or wireless. A person skilled in the art will alsoappreciate that all electronic communication in the system can be wired,all electronic communication in the system can be wireless, or someportions of the system can be in wired communication and other portionsof the system can be in wireless communication.

FIG. 1 is a perspective view of one embodiment of a surgical roboticsystem 300 that includes a patient-side portion 310 that is positionedadjacent to a patient 312, and a user-side portion 311 that is located adistance from the patient, either in the same room and/or in a remotelocation. The patient-side portion 310 generally includes one or morerobotic arms 320 and one or more tool assemblies 330 that are configuredto releasably couple to a robotic arm 320. The user-side portion 311generally includes a vision system 313 for viewing the patient 312and/or surgical site, and a control system 315 for controlling themovement of the robotic arms 320 and each tool assembly 330 during asurgical procedure.

The control system 315 can have a variety of configurations and it canbe located adjacent to the patient, e.g., in the operating room, remotefrom the patient, e.g., in a separate control room, or it can bedistributed at two or more locations. For example, a dedicated systemcontrol console can be located in the operating room, and a separateconsole can be located in a remote location. The control system 315 caninclude components that enable a user to view a surgical site of apatient 312 being operated on by the patient-side portion 310 and/or tocontrol one or more parts of the patient-side portion 310 (e.g., toperform a surgical procedure at the surgical site 312). In someembodiments, the control system 315 can also include one or moremanually-operated input devices, such as a joystick, exoskeletal glove,a powered and gravity-compensated manipulator, or the like. These inputdevices can control teleoperated motors which, in turn, control themovement of the surgical system, including the robotic arms 320 and toolassemblies 330.

The patient-side portion can also have a variety of configurations. Asdepicted in FIG. 1, the patient-side portion 310 can couple to anoperating table 314. However, in some embodiments, the patient-sideportion 310 can be mounted to a wall, to the ceiling, to the floor, orto other operating room equipment. Further, while the patient-sideportion 310 is shown as including two robotic arms 320, more or fewerrobotic arms 320 may be included. Furthermore, the patient-side portion310 can include separate robotic arms 320 mounted in various positions,such as relative to the surgical table 314 (as shown in FIG. 1).Alternatively, the patient-side portion 310 can include a singleassembly that includes one or more robotic arms 320 extending therefrom.

A robotic surgical system consistent with the present description canincorporate a visual sensor and/or camera and an associated viewingfield to allow the robotic surgical system to provide any feedback. Forexample, the robotic surgical system can include an end effector overwhich the system can have control. The system can provide instructionsto the end effector in the form of a declared action (e.g. clamping,energy delivery, etc.). Under ideal surgical conditions, the endeffector proceeds with performing the declared action as instructedbased on user input instructions. However, under many surgicalconditions, the end effector might not be able to perform the declaredaction as instructed for a variety of reasons and/or it might not beideal for the end effector to continue to perform the declared actionsfor a variety of reasons, such as tissue and/or end effectortemperature, proximity of the end effector to surrounding tissue,unexpected surgical conditions, human error, etc. The visual sensorand/or camera can be used to detect a variety of parameters of the tool,the end effector, and/or the surrounding tissue. If, for instance, anend effector is heated to an excess degree through use, the heatemanated by the end effector can cause damage to surrounding tissue ifthe heated end effector contacts or is kept in the vicinity of tissuefor too long a period of time. In such a situation, it can be desirableto have a predetermined distance threshold representing the closestdistance that the heated end effector can get to surrounding tissuewithout causing damage. The visual sensor and/or camera can also be usedto visually detect at least one visual indicator on the tool, onadjacent tools, and/or on tissue. For example, a visual indicatorindicative of a length scale can allow an action of the tool to bevisually measured by the camera and transmitted to a correspondingcontrol system, such as the control system 315 described above. Therobotic system can modify the action of the tool based on the visuallymeasured action.

FIG. 2 illustrates one embodiment of an electromechanical tool with ashaft 1503 having a distal end 1502 and an end effector 1504 mounted tothe shaft 1503 in the vicinity of patient tissue 1506. The end effector1504 includes jaws 1507, 1508, with jaw 1507 being in the form of anultrasonic blade. The shaft 1503 and the end effector 1506 are part of arobotic surgical system, such as the robotic surgical system 300illustrated in FIG. 1, and can be mounted on an electromechanical arm.The robotic surgical system can include an endoscope, such as binocularscope 1512, having at least one visual sensor 1510. The illustratedvisual sensor 1510 is disposed at a distal end of a binocular scope1512. The illustrated visual sensor 1510 is an infrared sensor, but thevisual sensor can be a CCD, a CMOS, or the like. The visual sensor 1510can be configured to detect the temperature T_(b) of at least part ofthe end effector 1504, for example of the ultrasonic blade 1507 of theend effector 1504, and/or the temperature T_(t) of the tissue 1506 ofthe patient that is adjacent the end effector 1504. In one aspects, acontroller can be configured to compare the temperature T_(b) of theultrasonic blade and the temperature T_(t) of the tissue of the patientand determine distance thresholds 1514, 1516 and 1518 for differenttemperatures of the end effector 1504. The distance thresholds 1514,1516 and 1518 can represent a variety of safe and/or non-harmfuldistances for the tissue 1506 and/or the end effector 1504, such as theclosest distance from the tissue 1506 of the patient that the heated endeffector 1504 can be positioned without causing damage to the tissue1506. For example, distance threshold 1514 can represent the closestposition an end effector 1504 having a temperature T₁ can be positionedwith respect to the tissue 1506 of the patient; distance threshold 1516can represent the closest position an end effector 1504 having atemperature T₂ can be positioned with respect to the tissue 1506 of thepatient; and distance threshold 1518 can represent the closest positionan end effector 1504 having a temperature T₃ can be positioned withrespect to the tissue 1506 of the patient. Temperature T₁ is less thantemperature T₂ which is less than temperature T₃. The temperatures T₁,T₂, T₃ can represent the temperature T_(b) of the ultrasonic blade 1507directly or can represent the compared temperatures between thetemperature T_(b) of the ultrasonic blade and the temperature T_(t) ofthe tissue. An infrared sensor, such as the Melexis MLX90621, can beintegrated into the binocular scope 1512 and/or the end effector 1504,and can act to compare the end effector temperature with an adjacenttissue temperature for an accurate indication of temperature. Thisprocess can occur before and/or during and/or after use of the endeffector to affect tissue. Force thresholds based on force limits canalso be used in addition to or instead of distance thresholds.

The controller, such as controller 315 illustrated in FIG. 1, can beconfigured to facilitate movement of the end effector 1504 toward thetissue 1506 of the patient. The controller can be configured todetermine a position of the end effector 1504 with respect to the tissue1506 of the patient through the visual sensor 1510. For example, thevisual sensor 1510 can obtain an image of the area in the vicinity ofthe end effector 1504 and/or shaft 1503. The visual sensor 1510facilitates determination of the position of the end effector 1504relative to the tissue 1506 of a patient through the use of one or morefixed-size and fixed-space indicators in the form of a visual scale,such as markers 1520 on the shaft 1503. The shaft markers 1520 can havea known thickness and a known separation between markers. Because thelengths and widths are fixed and known, the markers 1520 can be used todetermine a length scale and a relative position of the shaft 1503and/or the end effector 1504 to the tissue 1506 and/or the visual sensor1512. For example, the images of the markers 1520 can be triangulatedand used to determine the location of the shaft 1503 and/or the endeffector 1504 to the tissue 1506 and/or the visual sensor 1512.

The controller can therefore be configured to determine the location ofthe shaft 1503 based on detection by the visual sensor 1510 of the shaftmarkers 1520. During use, the controller can act to retard advancementof the end effector 1504 and/or the shaft 1503 toward the tissue 1506based on the sensed temperature of the end effector. For example, theend effector 1504 can be advanced toward the tissue 1506 whiletemperature is monitored. If the sensed temperature of the end effector1504 is at or in excess of a predetermined threshold temperature, forexample temperature T₁, the controller can act to stop the advancementof the end effector 1504 so that the end effector 1504 does not movecloser toward the tissue 1506 than a predetermined threshold distancefrom a tissue 1506, for example the distance threshold 1514. Because thethreshold distance 1514 represents the closest that the end effector1504 having a temperature T₁ can get to tissue 1506 without causingdamage, the controller can prevent harm to tissue 1506 by slowing orstopping the advancement of the end effector 1504. The thresholddistance and/or the threshold temperature can both vary depending on thesituation. For example, the sensed temperature of the end effector 1504may be at or above T₂ or T₃, and the controller may be configured tostop the advancement of the end effector 1504 so that the end effector1504 does not move closer to the tissue 1506 than the distancethresholds 1516 or 1518, respectively. While the temperatures in theillustrated embodiment represent comparisons between temperatures of theend effector and/or the ultrasonic blade and the surrounding tissue, thethreshold distances may be a function of the temperature of the endeffector 1504, the ultrasonic blade, and/or the surrounding tissuewithout comparison. In some variations, the end effector can move beyondthe set distance threshold even when a temperature exceeds a safethreshold, for example a manual override can be provided such that anoperator can force the end effector to move past the thresholds ifdesired.

Although an ultrasonic blade in the end effector 1504 is discussedherein, any end effector and/or any electromechanical tool can be used.The electromechanical tool can have a variety of configurations, such asbeing configured to apply energy to tissue engaged by the end effector,fire staples, and/or cut tissue.

In some variations, based on the size of the shaft markers 1520 asdetected at the visual sensor 1510, a determination can be made as tothe location of the shaft 1503 with respect to the location of thevisual sensor 1510. In some variations, based on a relative size ofpatient tissue and/or one or more other objects adjacent the patienttissue and/or the distal end of the shaft 1503, and the size of theshaft markers 1520, a determination can be made as to the location ofthe end of the shaft 1503 with respect to various surrounding objects,tissues, tools, etc.

While FIG. 2 illustrates measuring threshold distances from the endeffector 1504, distances can also be measured from surrounding tissue.For example, FIG. 3 illustrates the end effector 1504 in the vicinity oftissue 1506. However, threshold distances 1550, 1552, and 1554 aremeasured relative to tissue 1506 instead of the end effector 1504, as isillustrated in FIG. 2. A safe threshold distance of the end effector1504 from tissue 1506 can thus vary depending on the temperature of theend effector 1504. As illustrated FIG. 4, the controller can beconfigured to facilitate movement of the end effector 1504 toward thetissue 1506 of the patient at varying distances from the tissue based ontemperature. When the temperature of the end effector 1504 is at ahighest point (illustrated on the far left of graph 1700 of FIG. 4), theheated end effector 1504 is disposed at a location farthest from tissue1506 of the patient (illustrated on the far left of graph 1702 of FIG.4). Thus graph 1702 illustrates the T₂ distance threshold 1704. The T₂distance threshold 1704 is the closest distance that the heated endeffector 1504 having a temperature T₂ can get to the tissue 1506 of thepatient without causing damage. As the temperature of the end effector1504 reduces over time, the end effector 1504 can get closer to tissue1506 without damaging the tissue 1506. At 1706 the end effector 1504 isat a low enough temperature to be able to touch the tissue 1506 withoutcausing damage to the tissue 1506 (illustrated on the far right ofgraphs 1700, 1702). With reference to graph 1702, at time 1708 therobotic surgical system can be configured to stop the advance of the endeffector 1504 toward the tissue 1506 until the temperature of the endeffector 1504 has decreased further. For example, line 1710, illustratedin the graph 1702, represents the closest proximity of the end effector1504 with respect to the tissue 1506 of the patient when the temperatureof the end effector 1504 is below a temperature 1712. When thetemperature of the end effector 1504 has a temperature T₁, the roboticsurgical system can be configured to stop the movement of the endeffector 1504 toward the tissue 1506 of the patient at the distance1514. The distance 1514 is represented by the line 1710 in graph 1702 ofFIG. 4. At 1716, the robotic surgical system can be configured to haltthe movement of the end effector 1504 toward the tissue 1506. Dashedline 1714 of graph 1702 is an exemplary illustration of the velocity ofend effector 1504. As the end effector 1504 approaches tissue 1506, thevelocity of end effector 1504 can be configured to be reduced to ensurethe controller and the overall robotic system can stop the end effector1504 at selected distance thresholds. In some variations, an alert canbe provided to the operator of the robotic surgical system that theheated end effector 1504 has reached a threshold distance.

As discussed above, the robotic surgical system can be configured toallow manual override by the operator of the robotic surgical system.For example, the robotic surgical system can stop the end effector 1504at a particular distance threshold if the blade of the end effector 1504exceeds a desired temperature. The system can cause a signal or noticeto the operator, such as vibration of controls, visual and/or tactileand/or auditory feedback, etc., indicating that the system has stoppedall movement because a distance threshold has been reached. If theoperator wishes to reinstate motion and effectively ignore thethreshold, the system can be configured to receive an input from theoperator causing the robotic surgical system to move the end effector1504 closer toward the tissue 1506 of the patient than a thresholddistance would normally allow. Line 1718 of graph 1702 is an exemplaryillustration of the velocity of the end effector 1504 after manualoverride by the operator of the robotic surgical system. This situationmay be desirable for a variety of reasons, such as cauterizing cuttissue or an emergency surgical situation.

FIG. 5 illustrates another embodiment of a surgical tool with an endeffector 1802 coupled to a tool shaft 1804. The end effector 1802includes first and second jaws 1806, 1808. Jaw 1808 can be in the formof a cutting blade or jaw for delivering energy and cutting tissuegrasped between jaws 1806, 1808. A robotic surgical system with acontroller, such as robotic surgical system 300 illustrated in FIG. 1,can be configured to control the end effector 1802. The end effector1802 can couple with the tool shaft 1804 at a coupling 1812. Variousactuators can extend through the tool shaft 1804 for clamping the jaws.The controller can control and/or power a variety of functions in theend effector 1802. The end effector 1802 can be similar to the endeffector 1504, however, the end effector 1802 can incorporate one ormore sensors therein to assist in measuring temperature. For example, atemperature sensor 1816 can be disposed in the tool shaft 1804 at thecoupling 1812, temperature sensor 1818 can be disposed in the vicinityof a proximal end of the jaws 1806, 1808, and a temperature sensor 1822can be disposed within the jaw 1806 of the end effector 1802. Thesensors can take a variety of forms, such as thermocouples and/orinfrared sensors. For instance, the temperature sensor 1818 can be aninfrared sensor and can measure temperature at a portion 1820 of the jaw1808. The temperature sensors 1816, 1818, and/or 1822 can beelectrically connected to the controller. For example, a wire 1814disposed within the tool shaft 1804 can be configured to couple to oneor more sensors in the end effector. The controller can be configured toreceive signals generated by the temperature sensors 1816, 1818, and/or1822 including temperature information indicative of the temperature ofthe end effector 1802. The temperature information can then be used bythe controller to control movement of the end effector 1802 towardtissue, as described above regarding the end effector 1504. Temperaturereadings from visual sensors, such as infrared cameras, of objects thatare reflective and/or shiny, such as a cutting blade, can sometimes beless reliable than may be desired in an operating situation. In such asituation, temperature sensors incorporated into the end effector itselfand/or a shaft can assist the system to get accurate measurements. Forexample, a temperature sensor, such as thermocouple instrumentation,near a blade of an end effector can allow the system to take an accuratetemperature reading of the blade and proceed accordingly.

As illustrated in FIG. 6, in use, at least one type of energy can beapplied to a tissue using an end effector (such as any of the endeffectors described herein) formed on an instrument shaft of anelectromechanical tool. During application of the at least one type ofenergy to the tissue, a temperature of the end effector can be sensedand communicated to a controller. The sensed temperature can be used bythe controller to control movement of the tool shaft and/or end effectoras described herein. The sensed temperature can comprise a sensedtemperature of the end effector and/or a sensed temperature of thetissue surface. In some variations, the temperature can be sensed by asensor on the end effector itself. In some variations, the temperaturecan be sensed by a sensor on a camera. Based on the sensed temperature,a velocity of the end effector toward a tissue surface can be reduced.The movement of the electromechanical tool toward the tissue of apatient can be halted at distance thresholds from the tissue. Thedistance thresholds can be functions of the temperature of the endeffector as described above. In some variations, the velocity of an endeffector can be reduced to a first threshold velocity when thetemperature is within a first predetermined temperature range. The firstthreshold velocity can be adjusted in response to determining that theelectromechanical tool is at a first threshold distance from the tissuesurface. The velocity can be reduced to a second threshold velocity whenthe temperature is within a second predetermined temperature range. Thefirst threshold velocity can be adjusted in response to determining thatthe electromechanical tool is a second threshold distance from thetissue surface.

Visual sensors and/or cameras can be used to detect a variety ofparameters instead of or in addition to temperature. For example in someembodiments, visual sensors and/or cameras can be used to detect asensed amount of displacement of a tissue surface, a strain on thetissue of the patient, and/or other inserted tools during an operation.FIG. 7 illustrates a shaft 1903 of an electromechanical tool with an endeffector 1904 disposed on a distal end 1902 of the shaft 1903 in thevicinity of patient lung tissue 1906. The robotic system of FIG. 7 issimilar to the systems described above. The surgical system can includea controller, such as controller 315 illustrated in FIG. 1, operativelycoupled to the shaft 1903 and the end effector 1904, e.g., via anelectromechanical arm. In this embodiment, the controller can beconfigured to retard advancement of the end effector 1904 toward atissue surface 1930 of the tissue 1906 based on a sensed amount ofstrain or displacement of the tissue surface 1930.

A binocular scope 1912 can be used to view the shaft 1903 and the endeffector 1904. The shaft 1903 can include one or more fixed-size andfixed-space indicators in the form of markers. In the illustratedembodiment, the markers are in the form of spaced annular rings 1920 onthe shaft. In other embodiments, markers can be present on the endeffector. In the example illustrated in FIG. 7, the end effector 1904includes a cutting element (not shown) that travels through the endeffector 1904. A marker can be placed on the cutting element itself. Thebinocular scope 1912 can include one or more cameras 1910. Each camera1910 can obtain a separate image of the shaft 1910 and its markers 1920.Markers 1920 can have a fixed spacing. Each marking within the set ofmarkers 1920 can have a fixed width a, and the entire set of markers1920 can have an overall fixed width X₁. Because the lengths and widthsare fixed and known, the markers 1920 can be used to determine a lengthscale for images taken by the one or more cameras 1910. An applicator1932 can apply a material 1938, such as a particulate, onto the tissuesurface 1930. The one or more cameras 1910 can image the operating sitemore than once, and the system can compare the images and compare therelative positions of the material 1938 in successive images. Becausethe system has a length scale and can determine relative movement of thematerial 1938 in successive images, the system can use the material 1938to calculate an amount of displacement of the tissue surface 1930. Forexample, the displacement can be from a first position 1936 to a secondposition 1934, as illustrated in FIG. 7 using lung tissue. Two particles1940 a, 1940 b can be disposed on the surface of the tissue 1906. Whenin a deflated state the system can measure a first distance X_(2a)between the two particles 1940 a and 1940 b. When in an inflated state,the system can measure a second greater distance X_(2b) between the twoparticles 1940 a, 1940 b is X_(2b). By comparing the changes in the twostates, the system can determine displacement and/or strain on thetissue.

The sensed amount of displacement can allow the system to determine amaximum threshold position related to the measured displacement. Forexample, the system can compare the inflating and deflating lung tissuein FIG. 7 and determine that, between the first position 1936 and thesecond position 1934, the second position 1934 represents a maximumthreshold position of the tissue. By determining that tissue is at amaximum threshold position at position 1934, the system can affect oralter tool movement to have greater control and precision wheninteracting with the tissue. The analysis of the movement of theparticles can also facilitate determination of period movements of thetissue 1906. Consequently, anticipated organ position can be determinedand accounted for during manipulation of tissue and grasping of tissue.Similarly strain or force estimates can be used together with maximumthresholds to avoid over-stretch, over-stress, or tearing of tissue1906. For example, during lung adhesion dissection, a limit on tissuedeformation can be set so that if a user of the surgical systemapproaches the limit on tissue deformation, the surgical system cansound an alarm and/or generate a visual/tactile/etc. notification to theuser to prevent over-stretch. In some variations, the surgical systemcan be configured to stop the movement of any end effector if athreshold is exceeded.

A variety of different materials and/or particulates can be used. Insome variations, the material applied to tissue can be a bio-absorbableaerosolized particulate material and/or a high contrast material. Forexample, the contrasting particles can be 0.1 to 5 mm in size and madeof a biocompatible and absorbable material selected such that they willcause no or limited harm when left within the body. Examples of suchmaterials include absorbable polymers having a short degradationduration, sugars, or similar materials that will degrade and absorbwithin a relatively short time period. In some variations, materials canbe selected that absorb within 24 hours of application to avoid longterm inflammatory responses or risk of encapsulation or adhesionpromotion. Particulates can be absorbable polymer with dye, can bevicryl like, can include a sealant to ensure the particulates stick totissue, can be PCA, PLA, PGA, etc. A variety of sizes of particles canbe used, including particles that are too large to be applied through anaerosol application. While lung tissue is discussed herein, any tissueat a variety of different operation sites can be used.

The system can compare the relative changes between particulate fromsuccessive images and/or can determine an exact measurement of thevarious changes in displacement using the length scale from the markers1920. Because the lengths and widths of the markers 1920 are fixed andknown, the system can use the binocular scope 1912 with the one or morecameras 1910 to compare and contrast the markers 1920 with theparticulate positioning and/or the displacement of one or moreparticulates over successive images and determine an estimated size ofthe displacement, for example by using the dual focal length of thescope 1912 when at least two cameras 1910 are present. Similar to themarkers discussed above, the controller can also use the markers 1920and/or the material 1938 to determine a position of the end effector1904 relative to the tissue 1906. The controller can then retardadvancement of the end effector 1904 when the sensed amount ofdisplacement of the tissue 1906 is within a predetermined displacementrange, thus preventing accidental collision or less precise interactionbetween the end effector 1904 and any surrounding tissue.

The material 1938 can thus provide contrast points on the tissue 1906 ofthe patient, and images obtained by the one or more cameras 1910 canfacilitate determination of the movement of the tissue 1906 based on themovement of particles of the material 1938 relative to each other. Asmentioned, tissue strain can be determined for the tissue 1906 based onthe movement of the particles relative to each other. In somevariations, area and volume estimates can be determined based on thepositional information. As with positional information, changes in thearea and volume of tissue can be determined based on multiple imagestaken by the one or more cameras 1910 over time.

In various embodiments, particles provided in the material applied totissue can have a known size and geometry. For example, the geometry ofthe particles may include geometric shapes, rods with round balls on theends, or the like. As with the markers 1920 allowing determination of avisual scale, if the size and/or geometry of the particles are known, adistance between particles and movement of the particles can bedetermined. While a relative distance can be determined betweenparticles, an actual distance between particles and/or of variouslocations at an operation site can also be determined because of theknown size and/or geometry of the particles. This can allow kinematicanalysis and interpretation of the relative position and motion of theparticles and therefore the tissue. These particles can be used insteadof or in addition to markers on a tool. In some embodiments, particulatecan allow the system to create topographical representations of tissuesand/or operation sites.

In some embodiments, movement of tissue can provide information on whichsurgical instrument and/or what size instrument to use with the roboticsurgical system. For example, in embodiments using a cutting element andstapler in an end effector, a determination of what size staplercartridge to use can be made. Particulate in combination with markers ona shaft and/or end effector can be used to measure one or more atomicfeatures of the patient, place a scale with the field of view of thecameras, and/or as a safety measure for the surgical system to assuresafe stopping of the end effector as the instrument approaches tissue.

In addition to or instead of using markers on a tool to determine alength scale, an array of particles can be disposed on a tissue surfaceat an operation site to facilitate recreation of a three-dimensionalspace. For example, a calibration grid generator can be incorporatedinto the scope 1912 and generate a calibration grid on tissue using alaser-generated speckle pattern of known size and spacing. As with themarkers, the known size and spacing pattern can allow the system to makedeterminations regarding distances and orientations. Because thecalibration grid is on the tissue, the system can also makethree-dimensional determinations. The laser-generated speckle patterncan be part of the imaging system. The three-dimensional geometrycoupled with deformation of the tissue 1906 can facilitate revelation ofdissection planes of the tissue 1906 that would otherwise not bedetectable in a deflated state.

In some variations, a secondary light source can be used. An example ofa secondary light source may include an ultraviolet light source, aninfrared light source, or the like. One or more filters can be appliedto create the necessary contrast for visualization of tissue. Naturalsurface features of tissue can be used as trackable objects to furthercalibrate the surgical system and monitor the movement of tissue. In oneexample, synthetic particles can be used that are transparent underwhite light but provide contrast under a secondary light. In thismanner, the synthetic particles will not obscure the view of the user ofthe surgical system. A variety of end effectors can be used herein, suchas a cutting element and a stapler for cutting and sealing tissue,clamping jaws with an ultrasonic blade or jaws that deliver RF energy, asuturing end effector, etc. Along with using a variety of end effectors,a variety of additional tasks might be required depending on the endeffector used, such as automatically reloading a stapler incorporatedinto an end effector. U.S. Pat. No. 8,931,682, entitled“Robotically-Controlled Shaft Based Rotary Drive Systems For SurgicalInstruments,” filed on May 27, 2011, discloses surgical instruments andis incorporated herein by reference in its entirety. The markers and/ormaterials and/or particulates and/or grids on tools and/or tissuediscussed herein can be used in combination with determiningtemperatures as discussed herein.

In addition to the safety mechanisms discussed above, additional safetymechanisms are possible. For example, distance thresholds are not theonly mechanism possible for limiting movement of an end effector or toolto increase safety of surrounding tissue. A controller can limit largeand/or macro motions of an end effector while the end effector isengaged in fine and/or micro activities. For example, if an end effectoris being used to suture an incision such that a suturing needle isengaged in tissue, motions and/or activities and/or movements that wouldnot enhance the current activity of driving the suturing needle can bescaled back and/or entirely prevented. In other examples, if an endeffector is grasping, clipping, and/or otherwise tethered to tissue, anyhigh speed and/or large motions can be limited or otherwise scaled backuntil the tissue is released. This mechanism can prevent unintendedand/or potentially harmful movement to increase the safety of anoperation using the robotic systems provided herein. One or morewarnings can be provided to an operator so that the operator is aware ofthe limitations placed on movement. Similar to above, the warnings canbe any of a number of tactile, vibratory, auditory, and/or visualnotifications, such as being provided on a screen. The operator can thenchoose to override the mechanisms if desired based on the specificcircumstances of an operation. Because so much of the robotic systemsprovided herein depend on visual sensors and/or cameras, an automatedcleaning process of the visual sensor and/or camera can also beincorporated into any of the systems herein. U.S. Patent Pub. No.2008/0081948, entitled “Apparatus for cleaning a distal scope end of amedical viewing scope,” filed on Oct. 3, 2006, and U.S. Pat. No.8,915,842, entitled “Methods and devices for maintaining visibility andproviding irrigation and/or suction during surgical procedures,” filedon Jul. 14, 2008, disclose cleaning processes and are incorporatedherein by reference in their entirety. Automated cleaning of the visualsensor and/or camera can occur when foreign material is detected on animage.

There are several general aspects that apply throughout the application.For example, at least one surgical end effector is shown and describedin various figures. An end effector is the part of a surgical instrumentor assembly that performs a specific surgical function, e.g.,forceps/graspers, needle drivers, scissors, electrocautery hooks,staplers, clip appliers/removers, suction tools, irrigation tools, etc.Any end effector can be utilized with the surgical systems describedherein. Further, in exemplary embodiments, an end effector can beconfigured to be manipulated by a user input tool. The input tool can beany tool that allows successful manipulation of the end effector,whether it be a tool similar in shape and style to the end effector,such as an input tool of scissors similar to end effector scissors, or atool that is different in shape and style to the end effector, such asan input tool of a glove dissimilar to end effector graspers, and suchas an input tool of a joystick dissimilar to end effector graspers. Insome embodiments, the input tool can be a larger scaled version of theend effector to facilitate ease of use. Such a larger scale input toolcan have finger loops or grips of a size suitable for a user to hold.However, the end effector and the input tool can have any relative size.

A slave tool, e.g., a surgical instrument, of the surgical system can bepositioned inside a patient's body cavity through an access point in atissue surface for minimally invasive surgical procedures. Typically,cannulas such as trocars are used to provide a pathway through a tissuesurface and/or to prevent a surgical instrument or guide tube fromrubbing on patient tissue. Cannulas can be used for both incisions andnatural orifices. Some surgical procedures require insufflation, and thecannula can include one or more seals to prevent excess insufflation gasleakage past the instrument or guide tube. In some embodiments, thecannula can have a housing coupled thereto with two or more sealed portsfor receiving various types of instruments besides the slave assembly.As will be appreciated by a person skilled in the art, any of thesurgical system components disclosed herein can have a functional sealdisposed thereon, therein, and/or therearound to prevent and/or reduceinsufflation leakage while any portion of the surgical system isdisposed through a surgical access port, such as a cannula. The surgicalsystems can also be used in open surgical procedures. As used herein, asurgical access point is a point at which the slave tool enters a bodycavity through a tissue surface, whether through a cannula in aminimally invasive procedure or through an incision in an openprocedure.

The systems, devices, and methods disclosed herein can be implementedusing one or more computer systems, which may also be referred to hereinas digital data processing systems and programmable systems.

One or more aspects or features of the subject matter described hereincan be realized in digital electronic circuitry, integrated circuitry,specially designed application specific integrated circuits (ASICs),field programmable gate arrays (FPGAs) computer hardware, firmware,software, and/or combinations thereof. These various aspects or featurescan include implementation in one or more computer programs that areexecutable and/or interpretable on a programmable system including atleast one programmable processor, which can be special or generalpurpose, coupled to receive data and instructions from, and to transmitdata and instructions to, a storage system, at least one input device,and at least one output device. The programmable system or computersystem may include clients and servers. A client and server aregenerally remote from each other and typically interact through acommunication network. The relationship of client and server arises byvirtue of computer programs running on the respective computers andhaving a client-server relationship to each other.

The computer programs, which can also be referred to as programs,software, software applications, applications, components, or code,include machine instructions for a programmable processor, and can beimplemented in a high-level procedural language, an object-orientedprogramming language, a functional programming language, a logicalprogramming language, and/or in assembly/machine language. As usedherein, the term “machine-readable medium” refers to any computerprogram product, apparatus and/or device, such as for example magneticdiscs, optical disks, memory, and Programmable Logic Devices (PLDs),used to provide machine instructions and/or data to a programmableprocessor, including a machine-readable medium that receives machineinstructions as a machine-readable signal. The term “machine-readablesignal” refers to any signal used to provide machine instructions and/ordata to a programmable processor. The machine-readable medium can storesuch machine instructions non-transitorily, such as for example as woulda non-transient solid-state memory or a magnetic hard drive or anyequivalent storage medium. The machine-readable medium can alternativelyor additionally store such machine instructions in a transient manner,such as for example as would a processor cache or other random accessmemory associated with one or more physical processor cores.

To provide for interaction with a user, one or more aspects or featuresof the subject matter described herein can be implemented on a computerhaving a display device, such as for example a cathode ray tube (CRT) ora liquid crystal display (LCD) or a light emitting diode (LED) monitorfor displaying information to the user and a keyboard and a pointingdevice, e.g., a mouse, a trackball, etc., by which the user may provideinput to the computer. Other kinds of devices can be used to provide forinteraction with a user as well. For example, feedback provided to theuser can be any form of sensory feedback, such as for example visualfeedback, auditory feedback, or tactile feedback; and input from theuser may be received in any form, including, but not limited to,acoustic, speech, or tactile input. Other possible input devicesinclude, but are not limited to, touch screens or other touch-sensitivedevices such as single or multi-point resistive or capacitive trackpads,voice recognition hardware and software, optical scanners, opticalpointers, digital image capture devices and associated interpretationsoftware, and the like.

FIG. 8 illustrates one exemplary embodiment of a computer system 100. Asshown, the computer system 100 includes one or more processors 102 whichcan control the operation of the computer system 100. “Processors” arealso referred to herein as “controllers.” The processor(s) 102 caninclude any type of microprocessor or central processing unit (CPU),including programmable general-purpose or special-purposemicroprocessors and/or any one of a variety of proprietary orcommercially available single or multi-processor systems. The computersystem 100 can also include one or more memories 104, which can providetemporary storage for code to be executed by the processor(s) 102 or fordata acquired from one or more users, storage devices, and/or databases.The memory 104 can include read-only memory (ROM), flash memory, one ormore varieties of random access memory (RAM) (e.g., static RAM (SRAM),dynamic RAM (DRAM), or synchronous DRAM (SDRAM)), and/or a combinationof memory technologies.

The various elements of the computer system 100 can be coupled to a bussystem 112. The illustrated bus system 112 is an abstraction thatrepresents any one or more separate physical busses, communicationlines/interfaces, and/or multi-drop or point-to-point connections,connected by appropriate bridges, adapters, and/or controllers. Thecomputer system 100 can also include one or more network interface(s)106, one or more input/output (IO) interface(s) 108, and one or morestorage device(s) 110.

The network interface(s) 106 can enable the computer system 100 tocommunicate with remote devices, e.g., other computer systems, over anetwork, and can be, for non-limiting example, remote desktop connectioninterfaces, Ethernet adapters, and/or other local area network (LAN)adapters. The IO interface(s) 108 can include one or more interfacecomponents to connect the computer system 100 with other electronicequipment. For non-limiting example, the IO interface(s) 108 can includehigh speed data ports, such as universal serial bus (USB) ports, 1394ports, Wi-Fi, Bluetooth, etc. Additionally, the computer system 100 canbe accessible to a human user, and thus the IO interface(s) 108 caninclude displays, speakers, keyboards, pointing devices, and/or variousother video, audio, or alphanumeric interfaces. The storage device(s)110 can include any conventional medium for storing data in anon-volatile and/or non-transient manner. The storage device(s) 110 canthus hold data and/or instructions in a persistent state, i.e., thevalue(s) are retained despite interruption of power to the computersystem 100. The storage device(s) 110 can include one or more hard diskdrives, flash drives, USB drives, optical drives, various media cards,diskettes, compact discs, and/or any combination thereof and can bedirectly connected to the computer system 100 or remotely connectedthereto, such as over a network. In an exemplary embodiment, the storagedevice(s) can include a tangible or non-transitory computer readablemedium configured to store data, e.g., a hard disk drive, a flash drive,a USB drive, an optical drive, a media card, a diskette, a compact disc,etc.

The elements illustrated in FIG. 8 can be some or all of the elements ofa single physical machine. In addition, not all of the illustratedelements need to be located on or in the same physical machine.Exemplary computer systems include conventional desktop computers,workstations, minicomputers, laptop computers, tablet computers,personal digital assistants (PDAs), mobile phones, and the like.

The computer system 100 can include a web browser for retrieving webpages or other markup language streams, presenting those pages and/orstreams (visually, aurally, or otherwise), executing scripts, controlsand other code on those pages/streams, accepting user input with respectto those pages/streams (e.g., for purposes of completing input fields),issuing HyperText Transfer Protocol (HTTP) requests with respect tothose pages/streams or otherwise (e.g., for submitting to a serverinformation from the completed input fields), and so forth. The webpages or other markup language can be in HyperText Markup Language(HTML) or other conventional forms, including embedded Extensible MarkupLanguage (XML), scripts, controls, and so forth. The computer system 100can also include a web server for generating and/or delivering the webpages to client computer systems.

In an exemplary embodiment, the computer system 100 can be provided as asingle unit, e.g., as a single server, as a single tower, containedwithin a single housing, etc. The single unit can be modular such thatvarious aspects thereof can be swapped in and out as needed for, e.g.,upgrade, replacement, maintenance, etc., without interruptingfunctionality of any other aspects of the system. The single unit canthus also be scalable with the ability to be added to as additionalmodules and/or additional functionality of existing modules are desiredand/or improved upon.

A computer system can also include any of a variety of other softwareand/or hardware components, including by way of non-limiting example,operating systems and database management systems. Although an exemplarycomputer system is depicted and described herein, it will be appreciatedthat this is for sake of generality and convenience. In otherembodiments, the computer system may differ in architecture andoperation from that shown and described here.

Preferably, components of the invention described herein will beprocessed before use. First, a new or used instrument is obtained and ifnecessary cleaned. The instrument can then be sterilized. In onesterilization technique, the instrument is placed in a closed and sealedcontainer, such as a plastic or TYVEK bag. The container and instrumentare then placed in a field of radiation that can penetrate thecontainer, such as gamma radiation, x-rays, or high energy electrons.The radiation kills bacteria on the instrument and in the container. Thesterilized instrument can then be stored in the sterile container. Thesealed container keeps the instrument sterile until it is opened in themedical facility.

Typically, the device is sterilized. This can be done by any number ofways known to those skilled in the art including beta or gammaradiation, ethylene oxide, steam, and a liquid bath (e.g., cold soak).An exemplary embodiment of sterilizing a device including internalcircuitry is described in more detail in U.S. Pat. Pub. No. 2009/0202387filed Feb. 8, 2008 and entitled “System And Method Of Sterilizing AnImplantable Medical Device.” It is preferred that device, if implanted,is hermetically sealed. This can be done by any number of ways known tothose skilled in the art.

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

What is claimed is:
 1. A surgical system, comprising: anelectromechanical arm configured for movement in multiple axes; anelectromechanical tool having an instrument shaft and an end effectorformed thereon, the electromechanical tool being configured to bemounted on the electromechanical arm, and the electromechanical toolbeing configured to move with or relative to the electromechanical armand apply energy to tissue engaged by the electromechanical tool; and acontroller operatively coupled to the electromechanical arm and theelectromechanical tool, the controller configured to retard advancementof the electromechanical tool toward a tissue surface based on a sensedamount of displacement of the tissue surface.
 2. The surgical system ofclaim 1, further comprising an applicator having a material configuredto be applied onto the tissue surface, the material being configured toindicate the sensed amount of displacement of the tissue surface.
 3. Thesurgical system of claim 2, wherein the material comprises abio-absorbable aerosolized particulate material.
 4. The surgical systemof claim 1, wherein the sensed amount of displacement of the tissuesurface comprises a strain of the tissue surface.
 5. The surgical systemof claim 1, wherein the controller is configured to retard advancementof the electromechanical tool when the sensed amount of displacement ofthe tissue surface is within a predetermined displacement range.
 6. Thesurgical system of claim 1, further comprising a sensor configured tosense the amount of displacement of the tissue surface.
 7. The surgicalsystem of claim 6, wherein the sensor comprises a camera.
 8. A method ofoperating a surgical system, comprising: advancing an end effectorformed on an instrument shaft of an electromechanical tool toward atissue surface, the electromechanical tool being mounted on anelectromechanical arm; receiving a sensed amount of displacement of thetissue surface; and reducing, based on the sensed amount of displacementof the tissue surface, a velocity of the electromechanical tool towardthe tissue surface.
 9. The method of claim 8, wherein the sensed amountof displacement of the tissue surface is obtained by detecting movementof a patterned material deposited onto the tissue surface.
 10. Themethod of claim 9, wherein the patterned material provides at least twocontrast points.
 11. The method of claim 9, further comprisingdetermining a tissue strain based on the detected movement of thepatterned material.
 12. The method of claim 8, wherein the velocity ofthe electromechanical tool is reduced when the sensed amount ofdisplacement of the tissue surface exceeds a threshold amount ofdisplacement.
 13. The method of claim 8, wherein the velocity is reducedto a first threshold velocity when the sensed amount of displacement ofthe tissue surface is within a first predetermined displacement range.14. The method of claim 13, wherein the velocity is reduced to a secondthreshold velocity when the sensed amount of displacement of the tissuesurface is within a second predetermined displacement range.